Supercharger arrangement



Sept. 29, 1953 G. N coe-EQUAL 2,653,591

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SUPERCHARGER ARRANGEMENT Filed June 17, 194e 15v sheetsfsheet 12 ZBO SePt- 29, 1,953 G. N. COLE ETAL SUPERCH'ARGER RRNGEMENT 13 Sheets-Sheet 13 Filed June 17, 1948 Invezaors Gizmo nare III. Yale Patented Sept. 29, 1953 SUPERCHARGER ARRANGEMENT Gilmoure N. Cole, Manchester, and John S. Hasbrouck, Glastonbury, Conn., assignors to United Aircraft Corporation, East Hartford, Conn., a

corporation of Delaware Application June 17, 1948, Serial No. 33,468

Claims. (Cl. 12S-195) This invention relates to a supercharger arrangement for aircraft engines and particularly to an arrangement to converting an engine from a single stage of supercharge to two stages of supercharging.

It is advantageous in the production of a particularlengine model to be able to convert with as little modification as possible from a single stage of supercharging suitable for certain installations to two stages of supercharging foi other installations having different requirements. A feature of the invention is a power plant construction by which conversion from one to two stages of supercharging can be accomplished with a minimum of replacement parts.

Another feature is the arrangement of the rear crankcase section of an engine so that it may bev used with both a single-stage engine and a two-stage engine. One feature is the provision of side plates on the crankcase section which may be removed and replaced by the auxiliary superchargers and their drives. Another feature is the arrangement of a variable speed drive for the superchargers which is removable with the supercharger impellers.

Since the two stage engines may be used in a number of installations, a feature of the invention is the arrangement of the discharge conduits of the superchargers so that they may extend outwardly from the supercharger at any angle without modification of the power plant structure'. Another feature is the interchangeability of the opposite superchargers and housings for the auxiliary supercharger stage to permit a further variation of the direction of discharge of air from the superchargers.

`One feature of the invention is an arrangement ofthe parallel supercharger wheels of an auxiliary stage of supercharging with a common drive from the engine for both the main stage and the auxiliary stage. Another feature is the arrangement of sidewheeler superchargers operating in parallel to reduce the size of impeller required for delivering the necessary mass of air.

Another feature is the arrangement of the auxiliary superchargers as side-Wheelers with the auxiliary superchargers and the main supercharger all driven from a single centrally located driving gear. VOne feature is the provision for driving the auxiliary impellers at variable speeds from an accessory shaft located at right angles to the impeller shaft.

Other objects and advantages will be apparent from the specification and claims, and from the accompanying drawings which illustrate an embodiment of the invention.

Fig. 1 is a sectional view through an airplane nacelle showing an installation of the engine using a single stage supercharger.

Fig. 2 is a longitudinal sectional view through the rear section of the engine of Fig. 1.

Fig3 is a sectional view on a larger scale than Fig. 2 showing the .drive for the accessory shaft and for the secondary counterbalance.

Fig. 4 is a fragmentary sectional view of a part of the secondary counterbalance drive.

Fig. 5 is a sectional view substantially on the line 5 5 of Fig. 2. n

Fig. 6 is a sectional View substantially along the line 6 6 of Fig. 2.

Fig. 7 (Sheet .12) is a sectional view substantially along the line l-'l of Fig. 5.

Fig. 8 is a diagrammatic view in perspective of the accessory and supercharger drive mechamsm.

Fig. 9 is a" sectional view through the low vand intermediate ratio drives for the supercharger.

Fig. 10 is a view similar to Fig. 9 but showing a modification of the low and intermediate drives.

Fig. k11 is a view similar to Fig.v9 showing the high speed drive for the supercharger.

Fig. 12 is a view similar to Fig. l showing the engine installation with an auxiliary stage of supercharge. v

Fig. 13 is a perspective view showing the arrangement of the auxiliary supercharger stage.

Fig. 14 is a view similar to Fig. 2 showing the arrangement of the parts for the two stage supercharger drive.

l Fig. 15 is a perspective view'of the drives of Fig. 14.

Fig. 16is a sectional view substantially on the line |6-I6 of Fig. 14.

Fig. 17 is a sectional view substantially on the line l'l-Il of Fig. 14.

Fig. 18 is a fragmentary sectional view on a larger scale of the low-ratio drive of Fig. 1'7.

Fig. 19 is a perspective view showing the rear crankcase section with one side cover plate removed.

Fig. 20 is a view of one of the auxiliary stage supercharger casings showing the assembled drive.

Referring rst to Fig. 1, showing an engine with a single-stage of supercharge, the airplane nacelle 20 encloses an aircraft engine 22, supported as by a frame 24, the engine being connected to the frame as by mounting brackets 2'6. The engine shown is of the multiple-row radial type in which the crankcase 28 supports the cylinders 30 and has a nose section 32 incorporating the reduction gear, not shown, for the propeller system 34. The nose section also carries one or more accessories 36.

The crankcase 28 has a rear section 38 within which is enclosed the main supercharger and its drive together with a drive for other accessories 40, as will be hereinafter described in detail. The rear section has removable cover plates 4| on opposite sides thereof, to provide for conversion to a two-stage engine, as will appear later.

The nacelle has an air inlet 42 connected by a duct 44 to the carburetor 45. Air from this inlet may also be directed through an oil cooler 48. A flap 50 may be provided for closing the air inlet 42 and for opening the cooling air path 52, which surround the engine cylinders, to the duct 44.

As shown in Figs. 2 and 3, the engine crankshaft 54 journalled in the crankcase 28 is arranged to drive an accessory shaft 55 through a change-speed gearing such that the accessory shaft will rotate substantially faster than the crankshaft and preferably at a speed three times that of the crankshaft. To accomplish this, the end of the crankshaft has mounted thereon a cage 58, Fig. 3 which supports the shafts 80 cf a series of planet gears 82 (see Figs. 5 and 6), meshing with a sun gear 64 splined to the accessory shaft. The gears 62 also mesh with a ring gear 66 which is supported against rotative movement within a blower case or a housing 63 mounted on the end of the crankcase 28 and extending between the main crankcase 28 and the rear section 38. In this way, the accessory shaft 56 is driven at a speed greater than that of the crankshaft and at a selected speed determined by the sizes of the gears 82 and E4.

The drive mechanism, above described, also drives the secondary counterbalance '|01 which is journalled in the crankcase, being rotatably mounted on the crankshaft. Certain of the shafts 60 carried by the cage support, in addition to the gear 62, another gear l2 meshing with a sun gear 14 connected to the counterbalance. By selecting the proper sizes of gears 'I2 and 14, the desired ratio of speeds between the counterbalance and the crankshaft may be obtained; in the arrangement shown, the counterbalance rotates at twice the speed of the crankshaft.

Gear 14 has an inwardly projecting flange 15, Fig. 4, located between a surface T6 on the counterbalance 10 and a ring 80 splined to a hub 82 integral with the secondary counterbalance. A spring 84, engaging with the side of the ring 80 and held in position by a clamping nut 86, urges the ring 80 against the flange 15 and holds the flange 'E5 against the surface 15 on the counterbalance, thus frictionally damping the relative motion between the flange and the counterbalance. Flange l5 has slots 88, Fig. 6, to receive short springs 90, which, as shown in Fig. 4, extend into the recesses 82 and 04 in the secondary counterbalance and in the ring 80 respectively. These springs form a resilient drive between the flange l5 and the secondary counterbalance to absorb torsional pulsations in the drive from the crankshaft.

Although the ring gear 66 is supported against rotation, it is, however, resiliently supported circumferentially for the purpose of damping vibrations or pulsations in the driving mechanism. For this purpose, the ring 65, as shown in Fig. 5, has outwardly projecting lugs 95, each carrying a spherical element 90 tting in recesses in a plunger |08 slidable in guides |02 carried by a part of the blower case E8, Fig. 2. A coil spring |04 normally urges the plunger in such a direction as to urge the ring in a counterclockwise direction, Fig. 5.

The plunger |00 may forni a part of a da '.1- pot mechanism for further damping the motion of the ring. As shown in Fig. '7, the plunger |00 has a restricted orifice |06, which allows fluid to flow at a restricted rate rfrom one end of the cylinder |08, which is supported by the guides |02 and surrounds the plunger. The necessary supply of fluid will be retained within the cylinder through an inlet passage H0 connected to a suitable source of fluid. One end of the cylinder |08 is closed by a part of one of the guides |02; the other end is closed by a cap which also encloses spring |04. The speed increasing mechanism and the counterbalance drive are claimed in a copending Hasbrouck application Serial No. 33,515, filed June 17, 1923, now Patent No. 2,595,942.

With reference now to Figs. 2 and the accessory shaft 58, driven by the gear 64 which is splined to it, carries a driving gear 1|?. for the supercharger impeller H3. In the arrangement shown, gear ||2 is splined to the shaft 55 and forms a bearing surface for the shaft within a bracket ||4 bolted to a web H5 in the rear section 38. From the gear ||2 the drive is selectively through a gear H0 to a low ratio coupling ||0 or to an intermediate ratio coupling |20 and thence to a sleeve |22 surrounding the shaft 58 and carrying adjacent to its forward end the supercharger impeller I |3.

This impeller is located in the usual way within the blower case 68 and is surrounded by the diffuser disc |25, the latter being suitably connected to the blower case. Air enters through an inlet passage |28 from the carburetor 45, Fig. 1, and is delivered by the impelier into a chamber |30. From this chamber, the air under pressure reaches the individual engine cylinders through a series of intake pipes |32 connected to the blower casing and communicating, as will be apparent, with the inlet ports in the several engine cylinders. It may be noted that the inlet passage |28 is arranged at an acute angle to the axis of the impeller to minimise the change in direction of the air as it enters the impeller.

In addition to the low ratio coupling H8 and the intermediate ratio coupling |23, the supercharger may also be driven, as shown in Fig. 8, by a high ratio coupling |34. In each case, the drive is directly from the gear |42 on the accessory shaft. This shaft also functions to drive a number of accessories through other gears |35 and |38, as will hereinafter appear.

With reference to Fig. 9, which shows the low and intermediate ratio couplings, the gear I6 is splined to a jack shaft |40 to which is also splined the impeller |42 of the low ratio coupling and the impeller |44 of the intermediate coupling. The runner |45` of the low ratio coupling is splined to the hub of a gear meshing with a cooperating gear |50 on the sleeve |22. Similarly, the runner |52 of the intermediate ratio coupling is splined to the hub of a gear |54 meshing with a gear |55 on the sleeve |22. In the arrangement shown, the gears |50 and |56 are integral and are splined to the sleeve. It will be apparent that, by selectively admitting fluid to either the low or intermediate ratio couplings, the rate of rotation of the supercharger impeller I3 may be controlled.

As one means of introducing fluid selectively to the couplings, the shaft |40, which is journalled in the bracket I I4 and in a bearing |58 provided by the rear case 38 may be hollow to receive a sleeve |60 having 'a plug |62 between the inlet |64 to the 10W ratio coupling andthe inlet |66 to the intermediate coupling. Fluid' admitted into the closed end of the bearing recess |58, as through pipe |68, may enter the intermediate ratio coupling. Fluid admitted into the recess in the bracket |I4 is journalled, may flow through the sleeve |60 to the inlet to the low ratio coupling. Automatic'control valves I'iI and |12 for the couplings provide for cutting 'olf the oW to the coupling when the runner overspeeds the impeller.

Instead of the two separate couplings for the low and intermediate drives, it may be advantageous to utilize the modiiied construction of Fig. 10 in which the shaft 56 carries a gear |13 comparable to the gear I2. This gear is in mesh with a gear |14 on an intermediate shaft |16 journalled as is the shaft |48 in a bracket H4 and in a bearing |53 provided by the rear case. Shaft |16 carries a gear |18 in mesh with a gear |80 arranged to drive the sleeve |22 through an overrunning clutch |82, this drive constituting the low ratio drive for the supercharger impeller.

Also secured to the shaft |16 is the impeller |84 of a fluid coupling |85, the runnerl |86 of which is secured to the hub of a gear |88. Gear |88 meshes with a gear 90 which is splined to sleeve |22 and the hub of which forms a part of the overrunning clutch |82. Thus, if fluid is introduced into the coupling, as through the sleeve ISI within the shaft |16, it Will drive the gear |90 at a higher rate than the drive through the overrunning clutch so that the clutch begins to overrun and the supercharger impeller is then driven at the higher speed provided by the gear |88. This arrangement permits the elimination lof one of the hydraulic couplings where it appears to be advantageous.

As above stated, the impeller I3 may be driven at even higher speeds by the high ratio coupling |34 which supplements either of the low and intermediate ratios above described. To this end, the gear ||2 meshes with a gear |92, connected, as shown in Fig. 11, to the impeller |94, `of the coupling |34. The runner |96 is mounted on a shaft |98 journalled in bearings 200 provided by a cap 202 mounted on the side of the rear case. The shaft |98 has secured to it a gear 204 meshing with a gear 206 through which the supercharger impeller is driven. The gear 206 may be a part of the gear structure which includes gears |50 and |56. Cap 202 may replacevone of the side plates 4 I.

Referring now to Figs. 2 and 6, the accessory shaft 56 also drives a number of accessories, such as the scavenge pump 208 through the gear |36 and a cooperating bevel gear 2| 0. The latter gear is mounted on a shaft 2|2 journalled inthe rear case and in the bracket H4 and extending downwardly at an angle to the accessory shaft 56. Adjacent the lower end, the shaft 2|2 carries a bevel pinion 2| 4 meshing with a cooperating pinion 2| 6 on one of the shafts on the scavenge pump. By this arrangement it is possible to locate the scavenge pump adjacent to the lowermost part of the rear case. 'f

Other accessories are driven through the gear f |38 en the accessory shaft and through a cooperating gear ZIB on a Vjack shaft 220 journalled in a cover plate 222 attached centrally at the back. of the rear case and in bracket ||4. From the gear 2 I8 the drive may be through an interstarter.

`adjacent its discharge end.

mediate gear 224 on a jack shaft 226 journalled in the rear case and in the cap 222 and meshing with a cooperatingtgear 228, Fig.y8, which maybe connected, for example, 'to the starter. The gear 224 may also mesh with a gear 230, Fig. 8, journalled on a shaft232 and connected, for example, to a generator 233,' Fig. 2.

Instead ofthe customary cantilevering of'the accessories on a part of the crankcase, with resulting severe vibrations, certain of the accessories, such as the starter and generator, as shown in Fig. 2, are so mounted that they are supported for substantially their entire length. For example, the mounting boss 234 to which generator 233 'is attached, faces forwardly rof the rear crankcase section so that the generator extends along a part of the outer surfaceof the crankcase section 38 and is additionally supported'by projecting lugs 235 "integrally formed in. the crankcase section. I Associated with the gear 224 on the shaft 226, Fig. 8, may be another gear 236 driving a/gear 231 attached toa sleeve 238 journalled onv'the shaft 232. The sleeve may be connected, for exrample, to an hydraulicl or vacuum pump, not

shown.

The jack shaft 220 may also carry a pinion 239 meshing with a gear 240 on a jack shaft 242-. From the shaft 242the taeh0meter,'not shown, may be driven through cooperating gears 244'and 246 on shaft 242 and thetachometer shaft 241;, respectively. The gear 2|8` may' also mesh with a gear 248 on a jack lshaft 250 which carriesa driving gear 252 for gears 254 and 256 on fuel pump shafts 258 and' 260, respectively, through which fuel pumps may be driven. Other accesseries may be driven from the gear|38,. and, for

example, by means of an interm'eshing gear 262 through which, for example, an oil pressure pump may be driven.

It thus becomes apparent that the accessories are arranged'to be driven as a group/from the shaft 56 which, asvabove stated, is rotated atza speed higher than that ofthe crankshaft and preferably at the speed of the generator and It will be'pointed out hereinafter that the accessories are located in such a mannerthat an auxiliary supercharger stagel maybe addedto the rear case 38 without interfering with the accessory drive. The yparticular accessory. drive shown in'Figs. 2 and 8 are illustrative of `one arrangement of accessories and obviously, other arrangements may well be used as conditions require.

Referring again to Fig. 2, fuel may be supplied through ar pipe 264 extending through a'rpart `of the rear case and arranged to deliver fuelv to the spinner ring 266 located adjacentl the inlet end of the supercharger impeller II3. For additional delivery of fuel, the impeller maybe provided with one or more passages `268 fordeliveringfuel from the spinner 266 through the impeller toxbe discharged into the air owingfover the impeller The above-described engine,` is adapted to be converted from thel single stage of supercharge,

yas above described, to an k'engine having Itwo stages of supercharge without replacingxthe rear crankcase section 3B. As shown in Fig. 12, the engine is basically the same as in Fig. 1, beingxof the multiple row radial type with the crankcase 28 supporting the cylinders 30 and being located within the cowling of an engine nacelle 20; The supporting `frame 24'` is of somewhatv different construction than that of Fig. 1, althoughfzits purpose is the same. The rear section 28, which encloses the main supercharger and its drive, supports on opposite sides the casings 218 and 280 for the impellers of the auxiliary supercharger stage. As will be pointed out in detail later, these casings are attached on opposite sides of the rear case on the openings 26|, Figs. 16 and 19, normally closed by the cover plates 4|, Fig. l.

Air enters the auxiliary supercharger casings through ducts 282 and 284, Fig. 12, communicating with the centrally located inlet openings in the casings 218 and 280. Air compressed by the auxiliary compressor stages is discharged from the casings 218 and 280 into one or more intercoolers 286 and thence to the duct 44 leading to the carburetor 46 and to the main supercharger. A flap valve 288 may be provided in the duct 44 to close the discharge end of the intercoolers and to connect the main supercharger stage directly with the inlet 42.

Referring now to Fig. 14, the main supercharger impeller I|3 in the two-stage arrangement is driven from the accessory drive shaft 56 substantially in the manner above described with reference to Fig. 2. It will be noted, however, that instead of the variable speed drive utilizing fluid couplings, the gear H2 on the accessory shaft 56 meshes with a gear 290 on a jack shaft 292 journalled in a bracket 293 and in the bearing |58 in the rear case, and corresponding in general to the shaft |40. Shaft 292 carries a second gear 294 meshing directly with a gear 296 on the sleeve |22. Thus, the main supercharger impeller |3 rotates at a fixed ratio with respect to the engine speed. Bracket 293 replaces bracket ||4 of the single-stage engine.

The accessory drive for the two-stage engine is unchanged from that of the main stage and includes the gear 2|8 meshing with the gear |38 on the accessory shaft 56. The description of the single-stage engine accessory drives will sufice.

As shown in Fig. 15, the drive for the auxiliary stage impellers 298 and 300 is from the same gear ||2 that drives the main-stage impeller. Thus, the impellers 298 and 300 are mounted at opposite ends of a shaft 302 driven in the low speed range through a gear 304 meshing with the gear ||2 and a low-ratio hydraulic coupling 306 delivering power to a bevel gear 308 meshing with a gear 3|0 having a drive connection with the shaft 302. The auxiliary impellers are driven in the high speed range through a gear 3 l2 meshing with the gear |2 and in turn driving a gear 3|4. 'I'he latter drives a bevel gear 3|6 through the high ratio coupling 3|8, the bevel gear 3|6 meshing with a cooperating bevel gear 320 (see also Fig. 1'1) connected to the impeller shaft 302.

With reference now to Figs. 16, 17, and 18, the impellers 298 and 300 in the casings 218 and 280 are interconnected by the shaft 302 in such a way as to balance the thrust on the impellers without interfering with the meshing of the bevel gears. The shaft 302 includes a connecting rod 322 on the opposite ends of which sleeves 323 and 324 are mounted, endwise movement of the sleeves being limited by bolts 325 and 326 threaded into the ends of the rod and forming extensions of the rod. The bolts have clamping nuts 321 at the outer ends by which the sleeves are clamped securely to the connecting rod 322. The sleeves 323 and 324 have internal shoulders 328 engaging spacing rings 329 at the ends of rod 322.

The inner ends of sleeves 323 and 324 are interconnected by a quill 330 splined to both sleeves in such a manner that the sleeves will be driven in unison and may move axially within the tube. The sleeves 323 and 324, and the interconnecting rod 322 and bolts 325 and 326 form with the quill 330 the assembled shaft 302 connecting the impellers.

Each of the sleeves 323 and 324 has a hub 332 mounted thereon and having a spline connection 333 with the associated sleeve. Each hub has an annular flange 334 receiving a central boss 336 on the adjacent impeller for driving the impeller. Each impeller is preferably a shrink fit on the sleeve, and a clamping nut 338 additionally locks each impeller in axial position on the supporting sleeve.

For driving the shaft 302, the sleeves 323 and 324 carry surrounding sleeves 340 and 342 respectively, splined to and axially slidable on the sleeves 323 and 324 and forming bearing surfaces for the assembled shaft. The assembled shaft 302 is journalled centrally in bearings 344 in the bracket 293 mounted, as above stated, in the rear crankcase section 38. Adjacent each impeller, the assembled shaft is journalled in plates 346 and 348, respectively, which form the back walls of the impeller casings 218 and 280. These plates 346 and 348, as shown in Figs. 16, 1'1, and 18, fit on opposite sides of crankcase section 38, replacing the plates 4| of Fig. 1. In addition to providing bearings for the assembled shaft, the plates form the back closure plates for the casings 218 and 280. The front plates for the casings are the scrolls 341 and 349 attached at their outer edges to the plates 346 and 348 respectively.

The plates 346 and 348 are arranged to support the driving mechanisms for the auxiliary supercharger stage. Thus, as best shown in Figs. 17 and 18, the plates 346 provides bearings 350 and 352 for the shaft 354 for the low ratio drive. The plate 348 provides similar bearings 356 and 358 for the shaft 360 of the high ratio drive. With this arrangement, it is apparent that the auxiliary supercharger stage may be added to the engine on the same rear crankcase section 38 without the necessity for any modification of the crankcase section.

The drive connections for the low and high ratio drives of the auxiliary supercharger stage are similar, except for the gear ratios, and a description of the low ratio drive will suffice. As shown in Fig. 18, the gear 304 is splined to a sleeve 362 on which the impeller 364 of the hydraulic coupling 306 is mounted. The runner 366 of the coupling is splined to the shaft 354 to which the bevel gear 308 is also splined. The supply of fluid to the coupling may be through a passage 368 in plate 346 and through a ported plug 310 in the shaft 354.

Also, as shown in Fig. 18, the gear 3|0 driven from the gear 308 has a spline connection 31| with the sleeve 340 and is held in fixed axial position thereon by locking rings 312. The gear 3|0 is backed up by a thrust bearing ring 313 which engages with a cooperating ring 314 supported by plate 346 for limiting the axial movement of the gear. Gear 320 is fastened to sleeve 342 in a similar manner and is backed up by a thrust bearing 315. The assembled shaft 302. however, is free to slide axially within the sleeves 340 and 342, thereby permitting the axial thrusts on the opposite impellers 298 and 300 to be balanced.

In mounting the auxiliary supercharges on the rear crankcase section, the plate 346 with the low ratio drive mounted thereon is placed in position on the side of the crankcase section'33, being located as by pins 318, and is then fastened in position as by bolts'SlS. Bracket 293 having previously been mounted in position, sleeve 34D Will be in position with the gear 3m thereon meshing with gear 398. The plate 348 being similarly mounted, the shaft 362 is then assembled in position within sleeves 34S and 342 on the ends of which the impellers are mounted. Diffuser elements 38E! and 382 are placed around the impellers and the outer scrolls 34'! and 3dS of casings 21s and 285i are bolted to the backing plates 3% and 348 as by bolts or studs 335.

Although the auxiliary supercharger and its drive is shown as a sub-assembly in FigZU, `it will be understood that the showing is. for the purpose of clarity and the assembly is not rintended to be mounted as an assembled unit. The auxiliary superchargers are assembled on the rear crankcase section as above described, with plates 3% and 35,8 mounted on the side openings 28S provided in the rear crankcase section and covered, in the single stage engine, by the plates 4i.

With the arrangement of auxiliary superchargers shown, it is possible to have the discharge conduits 358 and on the supercharger casings N8 and 2S@ project substantially any angle in the plane of the casing by adjusting the angular position of the scrolls ad? and 349 on the backing plates Brit and 348. To accomplish this, the bolts 53e are evenly spaced around the periphery of the backing plate and the diffuser elements 38d and 332 which are piloted on backing plates 3dS and @fit respectively, in turn pilot the scrolls Set and Zitti in any angular position.

Also by reversing the positions of scrolls 3M and MS, that is by mounting scroll 349 on backing plate tdt, the tangential arrangement of the discharge conduits is reversed. Thus, as shown in Fig. 13, the impellers are rotating in such a direction that the air is moving counterclockwise and is discharged tangentially, whereas, in Fig. 12, the air, when the engine is viewed from. the same side, is moving clockwise and is accordingly discharged from the scroll in substantiallythe opposite tangential direction. Reversal ofthe scrolls necessitates reversal of the direction of impeller rotation, which can be readily done, as will 'be apparent.

Since the main impeller H3 and the auxiliary impellers 2% and Sti? are all driven from the gear i i2 which, being mounted on the accessory shaft, is driven faster than the crankshaft through the step-up gearing connecting the crankshaft and accessory shaft, the required step-up gearing at the impellers is minimized and the single stepup gear between the crankshaft and the accessory shaft serves ior all the impellers.

The other accessory drives are, as above stated, the same in both the single and two stage engines and no revisions of the accessory drive is necessary in replacing the single stage of supercharging by the two stage. It will be apparent that, in addition to the accessories above described, the rear plates 222 may have a small removable cap 332 which covers a power take on connected to the accessory shaft. As shown in Fig. 14, a coupling ted, which is splined to the end of the accessory shaft or to the hub of gear |38 and forms a bearing for the outer end of the accessory shaft, may carry internal splines 33B which will permit 10 the attachment thereto of a unit adapted to be driven from the accessory shaft.

It is thus apparent that, with a minimum of parts it becomes possible to convert from the single stage engine to a two stage engine. The removal of one of the cover plates di, 1, removes with it the high ratio drive for the main supercharger impeller. These plates are replaced vby the plates` 346 and 3&3, and the parts associated therewith, and make the engine a two stage unit. It will be understood that the particular controls by which the several ratios for the two stage supercharger is obtained is not a feature of the invention. The invention is rdirected to the structural arrangement of the engine 'by which to obtain the results above set forth.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and, described, but may be used in other ways without departure from its spirit as deiined by the following claims.

-We claim:

1. Inv an engine, a crankcase section, a power shaft longitudinally therein, opposed openings on opposite sides of the crank case, cover plates on said openings, a rear plate on said section, accessories on said rear plate, connections from said shaft ,to said accessories, a main stage super-A charger impeller in said crankcase section, and a drive from said shaft to said impeller including a gear on said shaft, in combination with opposed auxiliary stage superchargers arranged to be mounted on said opposed openings in place of said cover plates, each supercharger including an impeller and a mounting plate connected to the crankcase section and covering said opening and driving means for saidy auxiliary stage superchargers mounted on each of said mounting plates and having gears meshing with said gear on said shaft.

2. In an engine, a crankcase section, a power shaft longitudinally therein, opposed openings on opposite sides of the crankcase, cover platesy on said openings, a rear plate on said section, accessories on said rear plate, connections from said shaft to said accessories, a, main stage supercharger impeller in said vcrankcase section, and a. drive from said shaft to said impeller including a gear on said shaft, in combination with opposed .auxiliary stage superchargers arranged tovbe mounted on said opposed openings in place of said cover plates, each supercharger including an impeller and amounting plate connect- 'ed to the crankcase section and covering said opening, driving` means for said auxiliary stage superchargers mounted on each of said mounting plates and having gears rmeshing with said gear on said shaft, each 'ofsaid driving means including an hydraulic coupling, and a drive connection between the opposed supercharger impellers whereby both impellers may be driven by either of the driving means. i

3. In an engine, a crankcase section, a power shaft longitudinally therein, opposed openings on opposite sides of the crankcase adapted to be covered by cover plates, a rear plate on said section, accessories on said rear plate, connections from said shaft to said accessories, a main stage supercharger impeller in said crankcase section driven from said power shaft, and opposed superchargers mounted on Said opposed openings 4. In an engine, a crankcase section, a power shaft longitudinally therein, opposed openings on opposite sides of the crankcase adapted to be covered by cover plates, a rear plate on said section, accessories on said rear plate, connections from said shaft to said accessories, a main stage supercharger impeller in said crankcase section driven from said power shaft, and opposed superchargers mounted on said opposed openings, each supercharger including a mounting plate to cover said openings.

5. In an engine, a crankcase section, a power shaft longitudinally therein, opposed openings on opposite sides of the crankcase adapted to be covered by cover plates, a rear plate on said section, accessories on said rear plate, connections from said shaft to said accessories, a main stage supercharger impeller in said crankcase section driven from said power shaft, and opposed superchargers mounted on said opposed openings, each supercharger including a mounting plate to cover said openings, an impeller for each supercharger and a shaft transversely positioned in said crankcase section and interconnecting said impellers.

6. In an engine, a crankcase section, a power shaft therein, opposed openings on sides of the crankcase, a rear plate on said section, accessories on said rear plate, connections from said to said accessories, a main stage supercharger impeller in said crankcase section, a drive from said shaft to said impeller, and opposed auxiliary stage superchargers mounted on said opposed openings, each supercharger including an impeller, a mounting plate connected to the crankcase section covering an opening and driving means for said auxiliary stage superchargers driven by said shaft.

7. In an engine, a crankcase section, a power shaft therein, opposed openings on sides of the crankcase, a rear plate on said section, accessories on said rear plate, connections from said shaft to said accessories, a main stage supercharger impeller in said crankcase section, a drive from said shaft to said impeller including a gear on said shaft, and opposed auxiliary stage superchargers mounted on said opposed openings, each supercharger including an impeller, a

mounting plate connected to the crankcase section covering an opening and driving means for said auxiliary stage superchargers driven by said shaft and having gears meshing with said gear on said shaft.

8. In an engine, a crankcase section, a power shaft therein, opposed openings on sides of the crankcase, a rear plate on said section, accessories on said rear plate, connections from said shaft to said accessories, a main stage super- L charger impeller in said crankcase section, a drive from said shaft to said impeller including a gear on said shaft, and opposed auxiliary stage superchargers mounted on said opposed openings, each supercharger including an impeller, a mounting plate connected to the crankcase section covering an opening and driving means for said auxiliary stage superchargers driven by said 12 shaft and having gears meshing with said gear on said shaft, each of said driving means including a hydraulic coupling.

9. In an engine, a crankcase section, a power shaft therein, opposed openings on sides of the crankcase, a rear plate on said section, accessories on said rear plate, connections from said shaft to said accessories, a main stage supercharger impeller in said crankcase section, a drive from said shaft to said impeller including a gear on said shaft, and opposed auxiliary stage superchargers mounted on said opposed openings, each supercharger including an impeller, a mounting plate connected to the crankcase section covering an opening and driving means for said auxiliary stage superchargers driven by said shaft and having gears meshing with said gear on said shaft, each of said driving means including a hydraulic coupling, and a drive connection between the opposed supercharger impellers for driving both impellers by either of the driving means.

10. In an engine, a crankcase section having opposed lateral openings therein, cover plates arranged to cover said openings, and superchargers including an impeller, a shaft therefor, and a housing adapted to replace each of said cover plates, each housing covering one of said openings and being mounted on the crankcase section, a power shaft in said crankcase section having a first gear thereon, and means including a hydraulic coupling having driving and driven elements, a second gear associated with the driving element and adapted to mesh with said rst gear, a bevel gear connected to said driven element and a cooperating bevel gear on said impeller shaft, said coupling, second gear, and bevel gears being mounted on the housing and arranged to be located within the crankcase section when the housing is in position thereon.

GILMOURE N. COLE. JOHN S. HASBROUCK.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,647,434 Chorlton Nov. 1, 1927 1,874,681 Woolson Aug. 30, 1932 1,998,778 Gregg Apr. 23, 1935 2,001,866 Caminez May 21, 1935 2,098,718 Caminez et al. Nov. 9, 1937 2,172,100 Hoffman et al Sept. 5, 1939 2,238,889 Kollrnann Apr. 22, 1941 2,346,032 Kinnucan Apr. 4, 1944 2,393,172 Larrecq Jan. 15, 1946 2,400,307 Hobbs et al May 14, 1946 FOREIGN PATENTS Number Country Date 399,133 Germany July 28, 1924 528,774 Great Britain Nov. 6, 1940 

